DocumentCode :
1080900
Title :
Optimality and Duality of the Turbo Decoder
Author :
Regalia, Phillip A. ; Walsh, John MacLaren
Author_Institution :
Catholic Univ. of America, Washington
Volume :
95
Issue :
6
fYear :
2007
fDate :
6/1/2007 12:00:00 AM
Firstpage :
1362
Lastpage :
1377
Abstract :
The near-optimal performance of the turbo decoder has been a source of intrigue among communications engineers and information theorists, given its ad hoc origins that were seemingly disconnected from optimization theory. Naturally one would inquire whether the favorable performance might be explained by characterizing the turbo decoder via some optimization criterion or performance index. Recently, two such characterizations have surfaced. One draws from statistical mechanics and aims to minimize the Bethe approximation to a free energy measure. The other characterization involves constrained likelihood estimation, a setting perhaps more familiar to communications engineers. The intent of this paper is to assemble a tutorial overview of these recent developments, and more importantly to identify the formal mathematical duality between the two viewpoints. The paper includes tutorial background material on the information geometry tools used in analyzing the turbo decoder, and the analysis accommodates both the parallel concatenation and serial concatenation schemes in a common framework.
Keywords :
decoding; duality (mathematics); free energy; optimisation; statistical mechanics; turbo codes; constrained likelihood estimation; formal mathematical duality; free energy measure; optimization criterion; performance index; statistical mechanics; turbo decoder; Approximation algorithms; Belief propagation; Concatenated codes; Information analysis; Information geometry; Iterative algorithms; Iterative decoding; Maximum likelihood decoding; Maximum likelihood estimation; Performance analysis; Dual optimization; free energy minimization; information geometry; maximum likelihood estimation; turbo decoder;
fLanguage :
English
Journal_Title :
Proceedings of the IEEE
Publisher :
ieee
ISSN :
0018-9219
Type :
jour
DOI :
10.1109/JPROC.2007.896495
Filename :
4282130
Link To Document :
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